The present invention relates to a method of calibrating an integrated pressure management system that manages pressure and detects leaks in a fuel system. The present invention also relates to a method of calibrating an integrated pressure management system that performs a leak diagnostic for the headspace in a fuel tank, a canister that collects volatile fuel vapors from the headspace, a purge valve, and all associated hoses.
In a conventional pressure management system for a vehicle, fuel vapor that escapes from a fuel tank is stored in a canister. If there is a leak in the fuel tank, canister or any other component of the vapor handling system, some fuel vapor could exit through the leak to escape into the atmosphere instead of being stored in the canister. Thus, it is desirable to detect leaks.
In such conventional pressure management systems, excess fuel vapor accumulates immediately after engine shutdown, thereby creating a positive pressure in the fuel vapor management system. Thus, it is desirable to vent, or xe2x80x9cblow-off,xe2x80x9d through the canister, this excess fuel vapor and to facilitate vacuum generation in the fuel vapor management system. Similarly, it is desirable to relieve positive pressure during tank refueling by allowing air to exit the tank at high flow rates. This is commonly referred to as onboard refueling vapor recovery (ORVR).
A sensor or switch signals that a predetermined pressure exists. In particular, the sensor/switch signals that a predetermined vacuum exists. As it is used herein, xe2x80x9cpressurexe2x80x9d is measured relative to the ambient atmospheric pressure. Thus, positive pressure refers to pressure greater than the ambient atmospheric pressure and negative pressure, or xe2x80x9cvacuum,xe2x80x9d refers to pressure less than the ambient atmospheric pressure.
The present invention is achieved by providing a method.